This would be nice, I agree. I would also extend the feature to give the ability to both the thread creator and thread repliers to flag the thread as "currently being helped".
There are times when I'll provide assistance which turns out to be inadequate or misguided, but since the thread shows replies, it may be overlooked by others who could give a better answer. If I could flag the thread as "no solution yet", or revert it back to "Unresolved issue", then others would give it attention again.
Possible thread conditions: